Purpose:
To evaluate contrast sensitivity (CST), low contrast visual acuity (LCVA) & color perception under different illumination levels & pupil sizes after clear & yellow-tinted unifocal & multifocal acrylic IOL implants.
Methods:
Prospective clinic-based non-randomized controlled study. After providing informed consent, 43 patients [mean age 70.7±9.4 (sd)] underwent clear-corneal phacoemulsification by a single surgeon with one of four IOLs (SA60AT, SN60AT, SN60WF & SN60D3) and were tested with Pelli Robson contrast sensitivity (PRCST), sine-wave spatial frequencies (SF) 6 & 12 cpd (CSV 1000CVA test face), LCVA & Farnsworth-Munsell (FM) 100-Hue color test under standard conditions with best corrected visual acuity (BCVA). Testing was done four times - under 5 and 85 cd/m2 ambient illumination with dilated (mean 7.6 mm) pupils at 1 week & undilated (mean 3.8 mm) pupils 5 weeks after surgery. Patients with pre-existing color vision defects, decreased acuity for reasons other than cataract, post op BCVA less than 20/40 & total post op astigmatism greater than 2D were excluded. The FM 100-Hue software, Analysis of Variance with contrasts, paired T-tests & post hoc Bonferroni were used to examine statistical significance (SPSS 14.0)
Results:
When contrasted with the remaining hues, the FM test showed higher Blue-Green raw error scores with all IOLs. This was highly significant with SN60WF implants with both dilated (p=0.020) & undilated (p=0.000) pupils. There was no difference between the IOLs in total error scores, severity of color loss (Confusion index) or in the polarity of cap arrangement (Scatter index). All patients showed improved CST & LCVA with undilated pupils (p<0.05). There was no statistical difference between the IOLs in PRCST, SF 6 & 12 cpd & LCVA. All patients had statistically better PRCST (p<0.05) & 12.5% LCVA (p=0.001) under 85 cd/m2 room illumination.
Conclusions:
Higher errors are found in Blue-Green hue perception but are not limited to yellow-tinted IOLs. Brighter room illumination improves and dilated pupils worsen contrast sensitivity in all lenses including those with aspheric surfaces & multifocal optics.
Keywords: color vision • contrast sensitivity • intraocular lens